Mars Reconnaissance Orbiter HiRISE spies comet Siding Spring

Mars Reconnaissance Orbiter HiRISE spies comet Siding Spring

HiRISE caught these photos of comet Siding Spring on the spacecraft's last Mars orbit before the comet's closest approach, around 17:00 UTC on October 19. This composite image shows two versions of each of two of the best HiRISE images of the comet. Shown at top are images with the full dynamic range, showing the nucleus and bright coma near the nucleus. Shown at bottom are versions where the fainter outer coma is brightened, saturating the inner region. The images at left and right were taken about nine minutes apart. The comet turned out to be smaller than predicted.